Vehicle with weight sensing

ABSTRACT

An agricultural vehicle is provided with means for continuously sensing the weight of an accumulated payload and a GPS navigation system (18). Weight and positional information, and optionally also sensed vehicle speed, are analysed in an analysis/display unit (14) and a map generated of e.g. weight/hectare. The principal application is an agricultural trailer with payload weight sensors (15), towed by a tractor with GPS and analysis systems. A map of yield of e.g. a root crop may be generated as the crop is harvested and continuously deposited into the trailer as it moves along.

The present invention relates to the measurement of crop yield inparticular in the context of "yield mapping", that is to say themeasurement of crop yield as it varies over a field and the generationof a corresponding map showing the variation. The invention may alsohave other applications in the general "precision farming" field oftechnology, that is to say the capturing and using of yield and otherdata as distributed over an area of land and the automatic varying oftreatment of e soil or crops over a given area of land.

It is known to produce a "yield map" using a combine harvester fittedwith a grain yield meter together with a locating system. Many types of"yield meter" exist, most of which detect the volume flow of grainpassing through a combine harvester. One or two systems detect the massflow of grain, for example by a gamma ray absorption method or in oneproposed system by detecting the weight of the suspended end of an augercarrying harvested grain in a combine harvester; the weight of thesuspended end of the auger at any given time is directly representativeof the mass flow of grain being transported by the auger. All of thesesystems tend to be somewhat complex and are also specifically designedfor use in combine harvesters. It is an object of the present inventionto provide a system for detecting crop yield, and then producing a yieldmap, which is relatively simple and also applicable to a wide variety ofharvesting applications. In particular, it is an object of the inventionto provide a system for generating a yield map of a harvested field ofroot crop.

A further object of the invention is to provide an agricultural trailerwith meansfor continuously sensing the weight of its payload whilstmoving.

According to the invention, a vehicle comprises payload carrying meanscharacterised by:

a) Sensing means for continuously sensing accumulated payload weight asthe vehicle travels along;

b) locating means for establishing the position of the vehicle;

c) analysis means for automatically combining the sensed weight

information with the positional information to produce a map of thesensed weight, or a parameter derived therefrom, as distributed acrossan area over which the vehicle has travelled.

The term "map" as used here is intended to include not only a pictorialrepresentation of a parameter as distributed across an area, but alsothe equivalent information in electronic form, for example on a computerdisk.

It will be appreciated that a map of cumulative sensed weight will, ofitself, be little use. However, such information may be processed toproduce a map of the change of sensed weight per unit area. Whenharvesting a root crop, the crop is usually fed directly into a trailertowed behind a tractor as the harvester movesalong a field and thusweight change per unit area amounts to a direct indication of cropyield. However, the only "raw data" which needs to be acquired in thefield is an indication of weight and an indication of position. Thisinformation may then be processed at leisure, for example using anordinary office based PC.

It is preferable, however, for the data to receive more treatment "onthe go" and accordingly it is preferred that the said derived parameteris the rate of change of accumulated payload with either time ordistance, or alternatively is a further parameter derived from that.

It will be appreciated that the rate of change of payload with distancewill be directly proportional to the yield (i.e. weight per hectare).The rate of change of payload with time may be combined with theposition or speed information to derive weight per hectare, and afurther preferable feature is therefore a speed sensing means, the speedbeing used to generate the derived parameter.

Preferably, the derived parameter is generated using an average valuefor sensed weight, taken over a given time period, e.g. 1-100 seconds,preferably 5-60 seconds, more preferably 10-40 seconds, or still morepreferably 20-30 seconds.

In another aspect of the invention, an agricultural trailer is providedhaving a payload weight sensing system arranged to generate anelectronic output representative of accumulated payload weight or aparameter derived therefromas the trailer travels along.

Such a trailer may be used for a great many applications, but isparticularly suitable for use in the context of the first aspect of theinvention mentioned above.

Preferably, the trailer has mounted on it a low pass filter forfiltering out signals above a given frequency from the payload weightsensing system. This given frequency may be 5 Hz or higher, 10 Hz orhigher, or alternatively 15 Hz or higher.

The effect of the low pass filter is to filter out spurious highfrequency signals from the weight sensing system, e.g. signals caused byengine vibration from a tractor towing the trailer.

A further problem associated with sensing payload weight whilst on themove is the generation of spurious weight readings as the trailer movesacross uneven ground.

This problem may be largely overcome by means on the trailer foraveraging the sensed weight over a given time period, and such averagingmeans may therefore preferably be included in the trailer according tothe second aspect of the invention.

Another problem is the effect on the output of the weight sensing systemof the inclination of the trailer on sloping ground. and this can beovercome by providing some means for sensing ground slope and adjustingthe signal from the weight sensing means accordingly. For example, anelectronic inclinometer can be mounted on the trailer and the signalfrom this fed to a processor for adjusting the sensed weight signal.

Further features and advantages of the present invention will beapparent from the following description of one specific embodiment whichis given by way of example only with reference to the following drawingsin which:

FIG. 1 is a side elevation of a trailer in accordance with one aspect ofthe present invention; and

FIG. 2 is a schematic representation of a system for sensing payloadweight and producing a map.

Referring firstly to FIG. 1, an agricultural trailer suitable for beingtowed behind a tractor comprises a main chassis 1, wheels 2 and asubframe 3 pivoted to the main chassis at hinges 4. Mounted on thesubframe via load cells 5 is the trailer main body 6 which isessentially an open top box as in any conventional agricultural trailer.Mounted between the main chassis 1 and subframe 3 is a hydrauliccylinder 7 by means of which the subframe is tilted with respect to thechassis. An electronic unit 8 is mounted on the forward part of thetrailer and the functioning of this will be explained below. Anelectronicinclinometer 12 is mounted on the side of the trailer chassis1 and a speed sensor 13 is mounted on the rear axle of the trailer. Anadditional load cell (not shown) may optionally be mounted on thetrailer with a free hanging weight suspended from it; the purpose andfunctioning of such a load cell will be explained below.

The trailer differs from a conventional trailer in the inclusion of loadcells 5 and also the inclusion of the subframe 3 which would normally beunnecessary, but serves as a mounting point for the load cells 5 so thatthe cells carry all the weight of the trailer main body 6. Clearly, ifthe cells were connected between the main chassis 1 and the main body 6,part of the weight of the main body and any payload contained thereinwould be taken by the hinges 4 and hydraulic cylinder 7. The traileralso differs from a conventional trailer in the inclusion of aninclinometer 12 and speed sensor 13.

There are four load cells located at a distance of about 0.21 of thelength of the trailer main body from each end, a front and rear loadcell being mounted on each side of the trailer main body. Thisdistribution of load cells has been found to minimise bending effects onthe cells. It has also been found that this distribution of load cellsis reasonably tolerant to uneven loading in the trailer.

Turning now to FIG. 2, the outputs of the load cells 5, which areanalogueelectronic outputs, are connected in parallel (providing ameasurement of total load) to electronic circuitry 8, including amicroprocessor, arranged to sample the signal to the load cells at 20hertz.

This frequency was chosen to avoid aliasing effects from undulations inthe ground over which the trailer would, in practice, be towed. Givenground undulations of a maximum of 3 hertz, this constituted a samplingrate of over the accepted minimum of a factor of six times the signalfrequency

The circuitry 8 also includes a low pass filter acting directly on thesignal from the load cells 5, before any sampling takes place. This hasthe effect of removing higher frequency fluctuations produced e.g. bythe engine of a tractor to which the trailer is connected. In thisembodiment these fluctuations were most apparent at a tractor enginespeed of 900 rpm or 15 Hz, but this would of course vary with the typeof tractor used.

The electronic circuitry 8 includes means for converting the analoguesignals from the load cells into a single digital output, either inparallel or serial form to a port 9. This port 9 provides a connectionto a tractor analysis/display system 14 mounted in the cab of a tractortowing the trailer. The tractor system 14 includes a screen 16 and meansfor transferring data to or from a conventional data carrier, e.g. acomputer disk, inserted into a slot 17. The tractor system 14 isconnected to a GPS satellite navigation system 18 and includes amicroprocessorprogrammed with the necessary software to combineinformation received from the trailer via port 9 with the positionalinformation from the GPS system 18 to produce a map of weight data. Thismay be displayed on the screen or outputted to a data carrier.

The trailer electronics 8 include circuitry to average the previous fivehundred readings (i.e. a twenty five second period). This has the effectof removing most of any fluctuations in the reading of the load cellsdue to ground undulation.

The circuitry 8 includes a clock and generates values for rate of changeof weight with time at 1 second intervals, using the weight valueaveraged over the previous 25 seconds. In this way, discrete signalsrepresenting the average rate of change of weight over a 25 secondperiod are sent at a rate of 1 Hz to the tractor system 14 for analysis.This has been found to provide sufficient resolution for the purpose ofgenerating yield maps. However, more frequent signals, e.g. at 10, 20 or50 Hz could be outputted at port 9, alternatively.

It will be appreciated that the output at port 9 could alternatively besimply a continuous reading of cumulative weight (preferably a runningaverage over a few seconds, e.g. 25 seconds) and any processing toconvert this into information directly representative of yield could beperformed in the tractor system 14. Even the averaging stage could beperformed in the tractor. In

What is claimed is:
 1. An agricultural tractor that is operable in anagricultural field comprising:a chassis supported on a plurality ofwheels; a payload supported on said chassis and adapted to receiveproducts therein as the tractor is moved throughout the agriculturalfield; a weight sensor for generating a signal that is representative ofthe weight of the products in said payload; a position sensor forgenerating a signal that is representative of the position of thetractor in the agricultural field; and a controller that is responsiveto said signals from said weight sensor and said position sensor forgenerating a map of the weight of the products in said payload as afunction of the position of the tractor in the agricultural field. 2.The agricultural tractor defined in claim 1 wherein said weight sensorincludes a load cell.
 3. The agricultural tractor defined in claim 1wherein said weight sensor includes a plurality of load cells providedbetween said chassis and said payload.
 4. The agricultural tractordefined in claim 1 wherein said position sensor includes a globalpositioning satellite navigation system.
 5. The agricultural tractordefined in claim 1 wherein said controller is an electronic controller.6. The agricultural tractor defined in claim 1 wherein said controlleris responsive to said signals from said weight sensor and said positionsensor over a period of time for generating a map of the averaged weightof the products in said payload as a function of the position of saidagricultural tractor in the agricultural field.
 7. The agriculturaltractor defined in claim 1 wherein said controller is responsive to saidsignals from said weight sensor and said position sensor over a periodof time for generating a map of the average rate of change of weight ofthe products in said payload as a function of the position of saidagricultural tractor in the agricultural field.
 8. The agriculturaltractor defined in claim 1 further including a speed sensor forgenerating a signal that is representative of the speed of saidagricultural tractor, and wherein said controller is responsive to saidsignals from said weight sensor, said position sensor, and said speedsensor for generating a map of the weight of the products in saidpayload as a function of the position of said agricultural tractor inthe agricultural field.
 9. The agricultural tractor defined in claim 1further including means for adjusting the value of said signal from saidweight sensor in response to the inclination of said agriculturaltractor.
 10. The agricultural tractor defined in claim 1 furtherincluding an inclinometer for generating a signal that is representativeof the angle of said agricultural tractor, and wherein said controlleris responsive to said signals from said weight sensor, said positionsensor, and said inclinometer for generating a map of the weight of theproducts in said payload as a function of the position of saidagricultural tractor in the agricultural field.
 11. The agriculturaltractor defined in claim 1 further including an inclinometer forgenerating a signal that is representative of the angle of saidagricultural tractor, and wherein said controller is responsive to saidsignals from said weight sensor, said position sensor, and saidinclinometer for generating a map of the weight of the products in saidpayload as a function of the position of said agricultural tractor inthe agricultural field.
 12. The agricultural tractor defined in claim 1further including a supplemental weight supported on said chassis and asupplemental weight sensor for generating a signal that isrepresentative of said supplemental weight, and wherein said controlleris responsive to said signals from said weight sensor, said positionsensor, and said supplemental weight sensor for generating a map of theweight of the products in said payload as a function of the position ofsaid agricultural tractor in the agricultural field.